Fix loading KV quantization scale; Enable modelopt kv cache (#4686)

Co-authored-by: qingquansong <ustcsqq@gmail.com>

python/sglang/srt/models/grok.py

@@ -215,6 +215,7 @@ class Grok1Attention(nn.Module):
             num_kv_heads=self.num_kv_heads,
             layer_id=layer_id,
             logit_cap=logit_cap,
+            quant_config=quant_config,
         )
 
     def forward(